• Please review our updated Terms and Rules here

Netronics Explorer 85

falter

falter

Veteran Member
Joined
Jan 22, 2011
Messages
6,998
Location
Vancouver, BC
I finally got one of my holy grails.. an Explorer 85 in the actual Netronics chassis. It fires up and the monitor seems to work fine.

It appears to have the BASIC ROMs installed.. starting at C000. However, BASIC will not run. And in looking around I discovered the RAM contents of different address ranges are all the same. So 0000 to 0FFF is same as 1000 to 1FFF, C000 to CFFF and so on.

Does anyone know if the BASIC Netronics supplied required RAM expansion boards to be installed?
 
How are you keeping. I still owe you an email don't I!

The information I have found at https://worldradiohistory.com/hd2/I...0/Radio-Electronics-1980-05-OCR-Page-0081.pdf implies that the MS BASIC ROM requires levels B, D and E to be implemented. Level D provided for 4K RAM and level E stated that 'up to 12K RAM expansion could be available'. It doesn't state that the additional RAM was required for BASIC to operate.

I assume you have the manuals? If not, they are available here http://www.hartetechnologies.com/manuals/Netronics/ (but not the MS BASIC). Still looking for that.

Early static RAMS did exhibit consistent power-up contents - so I wouldn't worry just yet about the RAM contents. Do you have the onboard debug monitor working? If so, you can write and read unique values into the memory to see if they are OK or not.

There is a cheap and cheerful memory test program available somewhere to test for things like this.

EDIT: https://github.com/TomNisbet/Simple8085/blob/master/docs/explorer85-popelec1081.pdf states 'MS BASIC in ROM and a minimum of 4K RAM'. The 4K (I assume) must start at $0000.

Dave
 
Last edited:
I am keeping well, all things considered. Trust same for you? And you don't owe me anything! But I very much appreciate your help and insight for stuff like this. I did end up dumping 'the other half' of that 1702 EPROM for the Microkit machine - if it helps any. I wondered if you were able to 'decrypt' it. But there's no rush on that - not like we have software. I actually purchased a 1702 reader/writer kit and have been working on that intermittently so that might give better results anyway.

Yes I am thinking you are correct. IIRC if I have 8x2114s then I have about 4K of RAM, but perhaps it is not strapped the right addresses? I wonder if I could use my ProcTech 8KRA board... it is configured to start at $0000 - but I don't know how interchangeable S100 gear is - it was set up for my SOL 20.
 
And yes, I can use the monitor and attempt to edit memory contents but at $0000 and most ranges I've tried I cannot actually edit anything. I'm still trying to figure out what address space is available.
 
The default 256 bytes of RAM is at $F800 to $F8FF.

The monitor uses from $F8DC upwards, meaning that $F800 to $F8DB is available for you to use.

To modify some user memory:

.IF800
01
02
04
08
10
20
40
80
00
55
AA
FF
<ESC>

To dump the memory back:

.DF800,F81F

Check for equality as to what you entered.

Can you identify the revision of your Motherboard and any other boards you have in the system?

Can you also provide me with the settings for SW200 and SW201.

SW200 is for the EPROM base, SW201 is for the RAM base address.

SW201 settings seem to be dependent upon the revision of the PCB...

How are you attempting to start BASIC?

When you start BASIC, do you get the Microsoft Copyright notice or not?

EDIT: So I tracked down an interesting project at https://github.com/TomNisbet/Simple8085 giving me some clues as how to run BASIC.

Enter the following commands via the monitor:

.XS nnnn-F880 nnnn-C000
.G

Where nnnn is the current value of the Stack Pointer (SP) and Program Counter (PC) respectively. F880 sets the initial SP to the highest location within the original 256 bytes of RAM and C000 is the entry point of BASIC (Cold Start).

At this point, BASIC should ask for the memory size.

To achieve the correct ROM decode, links 1, 4 and 5 should be IN and others OUT at SW200.

For RAM at $000 then SW210 should be either 8, 5, 4 and 1 IN (Revision B or below) *** OR *** 8, 5, 3 and 1 IN (Later than Revision B - Revision 5 Motherboard?).

You should also be able to dump memory from the start of the BASIC ROM (.DC000,C020). I would bet that the first instruction should be an unconditional Jump ($C3).

Dave
 
Last edited:
Thanks Dave.

The revision of my board is D.

I can edit memory contents in the space you mentioned.. just not anywhere else.

Interestingly, SW200 and SW201 are all set to off.

https://drive.google.com/file/d/1du7F-U1Heq73CRsjDPj_IVCeCrf_t01y/view?usp=sharing

I did attempt to start BASIC using the instructions you mentioned - actually found a screenshot of someone else starting BASIC with similar commands, but when I do the G command it just freezes in place. No prompt ever happens.
 
Ah ha...

SW200 / SW201 being all off is no good...

I can't see a combination of SW200 (ROM base address) and/or SW201 (RAM base address) where all links being out (switches OFF) are a valid combination.

I can't see your google drive at the moment (I am at work) but I will look when I get back to my home machine...

You might want to try changing SW200 to 1, 4 and 5 ON only and SW201 to 1, 3, 5 and 8 ON only. This is based on the documentation I provided a link to back in post #2.

This should put the ROM at $C000 to $DFFF and the on-board 4K ram at base address $0000.

Level D Assembly manual for the configuration of SW201 (RAM).

Level E Assembly manual for the configuration of SW200 (ROM).

I see there are a few track cuts and wire links in the manuals to add the RAM. It may also be worth double-checking that all is well here and you haven't got any missing wires that have come adrift in the 30/40 years since this machine was last used!

Note in an earlier post (as I can't now edit it) I incorrectly referred to SW201 as SW210...

Dave
 
Last edited:
At home now :-)!

COVID-19: Work = spare bedroom (work IT - personal emails and file sharing sites forbidden). Home = downstairs on my Mac...

That picture is no good if you want to run BASIC...

Dave
 
Okay so I set the jumpers both ways you mentioned above... but yeah.. no change.

I decided just to do some perfunctory checks and verified the ROMs with my EPROM programmer using known good dumps of the BASIC from the hartetechnologies site. They verify 100%.

One thing I'm curious about though - when I dump C000, I get something that looks quite different from what the EPROM shows. I'm not sure if when looking at the EPROM I treat offset 00000000 as C000, but if I do, 0000000-0000000F reads like this:

F3 C3 04 C0 11 D3 C2 06 52 21 00 01 1A 77 23 13

But dumping C000 to C00F on the computer itself, I get:

C3 03 F0 3E 8D D3 F2 3E 09 32 F8 F8 D3 F8 AF 32

Think it should read the same as the reader has it no?
 
Yep, they should be four off 2K 2716 devices and we know they should reside at C000, C800, D000 and D800.

Let's concentrate on the EPROM side first and worry about the RAM later.

There is something that doesn't look right with your data... You are correct in that what you see in your EPROM programmer should be what you see within your EX85. Otherwise programming would be a 'crap shoot'...

Question, are the 2716 EPROMS identifiable as to which one should be at C000, C800, D000 and D800 (i.e. do they have labels attached)? Of course they do! You stated so in your previous post!

From my analysis, the C000 EPROM should be fitted into U300. C800 into U301. D000 into U302 and D800 into U303.

By each EPROM there are some links (S12, S13, S14 and S15). Can you confirm that each link is set for C-A? This connects pin 21 of the 2716 EPROM to VCC for correct operation.

The switch SW200 should be set as:

1, 4 and 5 as ON.
2, 3 and 6 as OFF.
7 and 8 as don't care (but set them OFF).

Don't forget that sometimes ON and OFF can be reversed by the switch manufacturer...

By rights, this should work... By 'work' I mean that you should be able to see from the monitor memory dump exactly the same as you see from your EPROM programmer.

The initial bytes of your dump from the EPROM programmer look sensible: F3 C3 04 C0 is DI; JMP C004.

The initial bytes of what the debug monitor thinks is at C000 (C3 03 F0) looks wrong to me (JMP F003). This is jumping back into the debug monitor as soon as it has entered BASIC?!

I therefore suspect that the EPROMs are physically installed in the wrong sockets - or there is something wrong with the address decoding logic for the EPROMS. We can work on this with an oscilloscope or logic probe and a bit of test software if it turns out to be the case.

If you dump a few bytes of memory from C000, C800, D000 and D800 in turn do you see the same byte pattern as you saw from your EPROM programmer?

A few things to be getting on with...

Dave
 
Last edited:
Just finished work for the day - so I will walk down the stairs back home and have a look at your photograph :-)!

Dave
 
Things look OK on the photograph from what I can see.

Let's see what happens if we enter a little program into the on-board Level A RAM (at $F800) via the debug monitor and execute it. The little program is:

Code: 
F800: 21 00 C0 ; LD HL,$C000
F803: 7E       ; LD A,(HL)
F804: C3 00 F8 ; JMP $F800

Please excuse the ZILOG mnemonics :-)...

If you execute this program, you should see a /CS operate on pin 18 of U300 (the $C000 ROM) but not on (a) any other pin 18 of any other ROM or (b) on any pin 8 of any 2114 RAM.

If you have a logic analyser, monitor the data bus (D7-D0) when the /CS of ROM U300 goes low ( pin 18 ) and look for the value of $F3 (which should be there according to your EPROM programmer dump).

You can change the byte at F802 of my little program from C0 to C8 to D0 to D8 to select each ROM in turn - and check that only the /CS appears on pin 18 of that specific ROM.

You will need to RESET the machine to halt it from the infinite loop.

Dave
 
I am slow today - too much RSX...

What you are dumping out at $C000 is the contents of the monitor ROM at $F000!

Now to find out why...

Dave
 
A couple of things:

1. Is IC U202 (74LS20) missing? It should definitely be installed as part of Level 'B'.
2. Can you tell me whether link S11 is made or not? It is open from the top - but is the link on the bottom of the board? It should only be linked for Level 'A' only - so this link should not be present.
3. Can you check for a wire link underneath the board from Z to U215 pin 5.
4. Can you check for a wire link from U105 pin 28 to J-2 pin 22.
5. Can you check the PCB tracking under both U206 and U207 to ensure the tracks are 'cut' between pins 3/4, 6/7, 9/10 and 12/13 of each IC.

Please don't modify the board if it is not in the state I am expecting. I may be wrong!

Dave
 
Last edited:
Hi Dave,

Unfortunately I had some family events so I didn't get to play with the Netronics machine much at all. I did install a 74LS20 (a few of them actually), just to see what would happen.. the system will not 'post' or reset with it in there. Only with it out.

I also lifted up the board and took a picture of the underneath. Note the broken yellow wire. I'm not sure that could have happened without someone cutting it, but it'd be odd to leave it there. The board seems to have been adhesived to the case so I don't see much opportunity for the wire to get broken with things shifting around. Not sure what's up with that.

https://drive.google.com/file/d/18at0nT3oyanlpjDhU0EFY49Ve8-HNYYA/view?usp=sharing
 
Hi,

No problem - stuff happens...

Interesting news about the 74LS20. I am sure this tells us something - but what I don't know at the moment.

I will take a look at the photograph after work.

Dave
 
You must log in or register to reply here.
Back
Top